Electron beam scanner utilizing labyrinth structure



ELECTRON BEAM SCANNER UTILIZING LABYRINTH STRUCTURE Filed April 27, 1967Sheet Jan. 7, 1969 o. E, HULTBERG 3,421,042

ELECTRON BEAM SCANNER UTILIZING LABYRINTH STRUCTURE Filed April 27, 1967Sheet g of 3 nwewrae. DONALD E. HULTBERG United States Patent 3,421,042ELECTRON BEAM SCANNER UTILIZING LABYRINTH STRUCTURE Donald E. Hultberg,Venice, Califl, assignor to Northrop Corporation, Beverly Hills, Calif.,a corporation of California Filed Apr. 27, 1967, Ser. No. 634,220 U.S.Cl. 315-12 12 Claims Int. Cl. H013 29/41 ABSTRACT OF THE DISCLOSURE Alabyrinth structure is formed from a series of plate members formingdynodes which are stacked one on top of the other. Each of such plateshas a channel or plurality of channels or apertures formed therein andon top of the uppermost plate is an electron target. At the verybottom-most portion of the labyrinth structure, a point source ofelectrons is installed. Separate switching means is connected to theopposite ends of the channels of each of the plates which allows anelectron accelerating potential to be alternatively switched to one orthe other of the ends of each of such channels. In this fashion, theelectron beam is directed through the labyrinth to any particulardesired portion of the target in accordance with the control signals fedto the switching means.

This invention relates to electron beam scanning devices, and moreparticularly to such a device of relatively flat and thin configurationwhich operates in response to a randomly addressed or sequential digitalcontrol signal. In co-pending application Ser. No. 511,747, filed Dec.6, 1965, for an electron beam scanning device, which is assigned toNorthrop Corporation, the assignee of the instant application, arelatively flat, thin electron beam scanning device is described whichoperates in response to a digital control signal and is capable ofrandom or sequential addressing. This type of device has many advantagesover cathode ray devices of the prior art, such as video camera tubes,video display tubes, memory and storage tubes, in that it provides acompact configuration having excellent linearity and definition which iscapable of both random and sequential addressing and is not subject toambient electrostatic and electromagnetic fields.

The device of this application, while having all of the advantages ofthe device described in the aforementioned co-pending application,additionally provides a number of significant additional advantages.Firstly, in the device of this invention, a point source of electronscan be used rather than a flat plate source. The use of a point electronsource in the device of the invention not only makes for more uniformelectron emission at the output but makes possible the use of agenerally commercially available type cathode which is both economicalto fabricate and easy to energize. Further, the rate of emission of apoint source of electrons is much easier to control than a broadsurfaced source. Also, in view of the fact that in the device of thisinvention a single electron beam is channeled through a labyrinth to thetarget, rather than a plurality of beams as in the device of theaforementioned pending application, a greater inherent electron beamintensity is feasible. Further, in the device of the invention there issubstantially less possibility of stray electrons inadvertently passingthrough the target due to the highly effective isolation provided by thelabyrinth structure. Still further, due to the much lower electronsecondary emission gain required in the device of the invention, loweraccelerating potentials are needed, lessening the insulation and powersupply requirements. Another significant advantage of the device of thisinvention is that there is less necessity for precise registration ofthe control dynodes forming the labyrinth.

The improvement is achieved in the device of the invention by forming alabyrinth structure with a plurality of control plates or dynodes whichare stacked one upon the other between a point source cathode member andan electron target. Each of the dynodes has a channel or a number ofchannels or apertures formed therein, the number of such channelsdoubling with each higher stacked dynode member as we approach thetarget. Separate electrodes are provided at each of the opposite ends ofthe channels of each dynode member and connected between the electrodesof each dynode member is a binary switching device for alternativelyreversing an electron accelerating potential between the pair of suchelectrodes. By controlling the switching of these switching devices, theelectron beam is channeled to any desired portion of the target toprovide an output signal thereon.

It is therefore an object of this invention to provide an improvedelectron beam scanning or addressing device.

It is a further object of this invention to provide an electron beamscanning or addressing device of relatively flat and compactconstruction utilizing a point electron source.

It is still a further object to provide an electron beam scanning oraddressing device utilizing a labyrinth structure for channeling anelectron beam between a point electron source cathode and a targetplate.

It is another object of this invention to provide an electron beamscanning device directly operable in response to a digital controlsignal which is capable of random addressing or sequential switching.

It is a further object of this invention to provide a high definitionelectron beam scanning device of compact configuration capable ofutilization as an image display, memory device, or image sensing device.

Other objects of this invention will become apparent from the followingdescription taken in connection with the accompanying drawings, ofwhich:

FIG. 1 is an exploded view of plate elements of a preferred embodimentof the device of the invention schematically illustrating the operationthereof,

FIG. 2 is an exploded view of the preferred embodiment of the device ofthe invention, and

FIG. 3 is a schematic diagram illustrating electronic circuitry whichmay be utilized to provide power and signals for the device of theinvention.

Referring now to FIG. 2, a preferred embodiment of the device of theinvention is illustrated. Dynode members 4 in the form of plates, whichare fabricated of an insulating material such as glass, have channels orapertures 4a formed therein. The dynode plates 4 further have resistivecoatings 4b on their upper and lower surfaces which may be of a materialsuch as reduced lead or other suitable material which has secondaryemission characteristics. The surfaces of the sides of channels 4a arealso coated with resistive secondary emissive material. In the channel4a of the lowermost dynode, point electron source cathode 11 which maybe of the thermionic variety is installed. Adjacent to the uppermostdynode is a target 50 which may be a phosphorescent display, a memory ora sensor plate. The number of channels 4a in plates 4 increase in binaryfashion as we proceed from cathode 11 to target 50, such channels beingarranged so that each pair of channels is bridged by a single channel inthe next lowest dynode.

Embedded in each of the dynodes 4 are electrical conductors 40. Each ofsuch conductors forms an electrode making contact to the secondaryemissive wall coating at each of the ends of channels 4a. Each of plates4 may be for-med from two separate plate units with the conductors 4cformed by electro-deposition techniques on the surface of one of theseplate units and sandwiched between the two plate units.

The plates 4 are stacked together with the channels therein forming anelectron labyrinth between cathode member 11 and target member 50 whichis utilized to address the beam to any desired portion of target 50 asnow to be explained in connection with FIG. 1.

In FIG. 1, different and separate numerals are utilized to identify thevarious parts of each of the plates shown to specifically identify anddistinguish the separate components thereof, this to facilitate thecomprehension of the operation of the labyrinth. FIG. 1 is a schematicview showing only a few of the plates that would be utilized in a normaloperative device, the explanation of the function of these few platesillustrating the principles of the invention.

Cathode 11 emits a beam of electrons 15 into channel 12. This beam isaccelerated towards anode 18 at the end of the channel by virtue of thepositive potential at such anode. Anode 18 is formed by conductive strip17 to which a positive potential is applied. A control electrode forcontrolling the intensity of electron beam 15 is formed by strip members20 to which are applied a control potential.

Plate member 23 has a single channel 25 formed therein with conductivestrip members 22 and 21 forming anodes 26a and 26b respectively atopposite ends of channel 25. Control flip-flop 29 is connected betweenstrip members 21 and 22.

Plate member 33 has two channels 36 and 37 which run normal to channel25. Anodes 38b and 3% are formed by strip member 41 on one end ofchannels 37 and 36 respectively, while anodes 39a and 38a are formed onthe opposite ends of these channels by strip member 42. Controlflip-flop 40 is connected between strip members 41 and 42 and providesthe preselected accelerating potential to these strip members. Controlflip-flop 29 is alternatively driven to either provide an electronaccelerating potential toward strip member 21 or toward strip member 22.Similarly control flip-flop 40 is alternatively driven to either providean accelerating potential toward strip member 41 or strip member 42. Thepositive potential outputs of flip-flops 29 and 40 are such that higheraccelerating potentials are provided to strip 41 or 42 than to strip 21or 22.

Let us assume now, for example, that flip-flop 29 is driven to providean accelerating potential to anode 26a, while flip-flop 40 is driven toprovide an accelerating potential to anodes 38a and 39a. Under suchconditions the electron beam 15 is initially accelerated towards anode18, which is directly below the central portion of channel 25. Theelectron beam strikes anode 18, emitting secondary electrons, which aredrawn into channel 25. From this point, the beam is accelerated towardsanode 26a where it is directly below the central portion of channel 37.Again, secondary electrons are emitted at anode 26a which are drawn intochannel 37, from where the beam is accelerated towards anode 38a.Secondary electrons emitted at anode 38a are then accelerated towardstarget 50.

The electron beam path through the labyrinth formed by the dynodes isalso illustrated in FIG. 2, which shows a greater number of dynodemembers forming the labyrinth structure. It thus can be seen that byplacing a flipfiop between each pair of strip members 4c (FIG. 2) thatthe beam can be addressed to any predesired portion of target 50, thedynode members forming an effective electron labyrinth for channelingthe beam in response to the control signals.

Referring now to FIG. 3, control circuitry which may be utilized tocontrol the channeling of the electron beam through the labyrinth isschematically illustrated. Voltage divider 60 comprises a plurality ofresistors 6041-60] and is connected between the positive and negativeterminals of DC power source 61. The positive terminal of power source61 is connected to target 50 while the negative terminal of the powersource which is normally grounded is connected to cathode 11. Transistorflip-flops 29, 40, 45 and 65, there being one such flip-flop unit foreach of the dynodes 4 forming the labyrinth, are connected at succeedingpoints along voltage divider 60, the emitters of each transistorflip-flop pair :being connected to a separate voltage divider point.

The collector of transistor stage 29a is connected to control strip 22of labyrinth plate 23, while the collector of transistor stage 2% isconnected to control strip 21 of this plate. The base electrodes oftransistor stages 29a and 2% are connected to receive the output ofaddressing logic control 63 which operates in response to clock signalsource 64.

In accordance with the output of clock signal source 64, the addressinglogic which includes conventional logical control circuitry willalternatively provide a signal to either transistor stage 29a or stage29b to actuate one or the other of these transistors. When transistorstage 29a is turned off, the collector of this transistor will assumethe potential of the flip-flop supply voltage (+2E) thereof and thus thevoltage divider potential at the point between resistors 60b and 600will be applied to control strip 22. Alternatively when transistor stage29b is turned on, this control potential will be applied to controlstrip 21. In this manner, the electron beam is directed to one or theother of the ends of channel 25 as described in connection with FIGS. 1and 2. In similar manner, each of transistor stages 40, 45 and 65provide a control signal to the control strips of a separate one of thelabyrinth plate members, in response to the addressing logic receivedthereby from addressing logic control 63 in response to clock signalsource 64. Thus it can be seen that beam 15 can be addressed to anydesired portion of target 50' in response to a control signal. It is tobe noted that the control circuitry illustrated in FIG. 3 is shown forexemplary purposes only, and that other control means may be employed toactuate the plate members to address the electron beam through thelabyrinth structure in the desired manner. It is also to be noted thatthe dynodes are shown as gray coded areas whereas conventional binary orother coding could be used.

The device of the invention thus provides a unique electron labyrinthstructure which can be effectively utilized for addressing an electronbeam generated by point source cathode to a target plate.

While the device of the invention has been described and illustrated indetail, it is to be clearly understood that this is intended by way ofillustration and example only and is not to be taken by way oflimitation, the spirit and scope of this invention being limited only bythe terms of the following claims.

I claim: 1. In an electron beam scanner, said scanner including meansfor emitting electrons, a target for receiving said electrons and apotential source connected between said electron emitting means and saidtarget for accelerating the flow of electrons between said electronemitting means and said target, means for addressing the electrons topredetermined portions of said target comprising a plurality of dynodemembers stacked one on the other between said electron emitting meansand said target, each of said dynode members having apertures providingchannels formed therein in a predetermined pattern, said dynode memberscombining to form an electron labyrinth between said electron emittingmeans and said target, means for alternatively applying an acceleratingpotential to one or the other of the opposite ends of the apertures ofeach of said dynode members, and

means for controlling the application of potential to said aperture endsin a predesired manner,

whereby an electron beam originating at said cathode is directed throughsaid labyrinth structure to a predetermined portion of said targetmember.

2. The scanner as recited in claim 1 wherein said dynode members eachcomprise a flat plate fabricated of an insulating material, said platesbeing coated on the surfaces of both sides and the channels thereof witha resistive secondary emissive material.

3. The scanner as recited in claim 1 wherein said dynode memberapertures are in the form of longitudinally extending strips.

4. The scanner as recited in claim 1 wherein each succeeding dynodemember has double the number of channels as the dynode member nextclosest to the electron emitting means.

5. The scanner as recited in claim 4 wherein pairs of channels of saiddynode members are each bridged by a single channel in the adjacentdynode member closer to the .electron emitting means.

6. The scanner as recited in claim '1 wherein said means foralternatively applying an accelerating potential to one or the other ofthe ends of the dynode member channels comprises a power source andbinary switching means for alternatively connecting the potentialoutputs of said power source between the ends of said dynode memberchannels in a first direction or a direction opposite said firstdirection.

7. The scanner as recited in claim 6 wherein said means foralternatively applying an accelerating potential to said dynode membersadditionally includes conductors embedded in said dynode members forconnecting the ends of said channels to said binary switching means.

8. The scanner as recited in claim 6 wherein said power source includesa voltage divider having a plurality of voltage taps thereon and saidbinary switching means comprises a plurality of flip-flop units, each ofsaid flipflop units being connected between a separate pair of voltagetaps on said voltage divider.

9. In an electron beam scanner, said scanner including means foremitting electrons, a target member for receiving said electrons and apotential source connected between said means for emitting electrons andsaid target for accelerating the flow of electrons therebetween, theimprovement including means for addressing the electrons topredetermined portions of said target comprising an electron labyrinthfor channeling said electrons between said electron emitting means andsaid target, said labyrinth comprising a plurality of substantially flatdynode members stacked on each other between said electron emittingmeans and said target, each of said dynode members having a plurality oflinear channels formed therein and passing through the broad surfacesthereof, said dynode members each having double the number of channelsas the adjacent dynode member closer to said electron emitting means,

means for alternatively applying an accelerating potential to one or theother of the opposite ends of said dynode channels, and

means for controlling the application of said accelerating potential tosaid channel in accordance with a control signal.

10. The scanner as recited in claim 9 wherein pairs of said dynodemember channels are bridged by single channels in the dynode member nextclosest to said electron emitting means.

11. The scanner as recited in claim 9 wherein said dynode members eachcomprise a flat plate fabricated of an insulating material, said platesbeing coated on all the surfaces except the outer edges thereof with aresistive secondary emissive coating.

12. The scanner as recited in claim 9 wherein said means foralternatively applying an accelerating potential to one or the oppositeends of the dynode channels comprises a power source and binaryswitching means for alternatively connecting the potential outputs ofsaid power source between the ends of said channels in a first directionor a direction opposite said first direction.

References Cited UNITED STATES PATENTS 3,005,127 10/1961 Aiken 3l5-18FOREIGN PATENTS 932,212 7/1963 Great Britain.

RODNEY D. BENNETT, Primary Examiner. C. L. WHITHAM, Assistant Examiner.

U.S. Cl. X.R. 315-18

